Its true they are so similar that they are hard to tell apart. So J decided to post them up for everyone to tell their differences.

Below are some pictures of their close ups.

As you can see from the side angle of the bottles, (Front to Rear, 37, 38, 39, 40)
#37 is creme white with Orange , Green, Yellow Flakes
#38 is clear white with Orange, Green, Yellow
#39 is clear white with Green, Blue flakes
#40 is clear white with Blue, Green flakes
Note: #39 and 40 are very similar if you put the bottles side by side. But we can see the different once we apply them on.

Pictures worth a thousand words. Below, you will see #37-40 apply on top of Nfu Oh #132 (Black).

From Left to Right: #40, 39, 38, 37.

Nfu Oh #37

Nfu Oh # 38

Nfu Oh #39

Nfu Oh #40

J hopes these will help you on choosing the right 37-40 selections ^_^.